不知道为什么错了

#include<bits/stdc++.h>
using namespace std;
struct student{
	string name;
	int C,M,E;
};
void bi(student a,student b){
	if(a.C+a.E+a.M<b.C+b.E+b.M){
		a.name="";a.name=b.name;
		a.C=b.C;a.E=b.E;a.M=b.M;
	}
}
int main(void){
	int N;
	scanf("%d",&N);
	student best;
	for(int i=1;i<=N;i++){
		student stu;
		cin>>stu.name>>stu.C>>stu.M>>stu.E;
		bi(best,stu);
	}
	cout<<best.name<<" "<<best.C<<" "<<best.M<<" "<<best.E<<endl;
	return 0; 
}